The present invention relates to a cutting device that can cut an object formed of a single member, such as glass, ceramics, resin, metal, or the like, or a composite member thereof continuously using one kind of cutting tool. More particularly, the present invention relates to a cutting device that cuts an object while smashing the very surface area of the object by allowing an impacting body formed of a hard solid body to impact on the object at a high speed with a high frequency, and to a cutting method using the same.
Generally, methods used for cutting and disassembling glass used in a cathode-ray tube (CRT) (herein after referred to as xe2x80x9cCRT glassxe2x80x9d) for the purpose of its recycling include a method of utilizing the thermal shock obtained by winding a heater wire around the CRT and energizing the heater wire to heat the CRT, a cutting method of using a diamond wheel cutter that is rotated at a high speed, a gas fusion cutting method (a method of melting and cutting glass using a gas), or the like.
Generally, sheet steel pieces (cold rolled steel plate sheets and strips cut to length or the like) forming bodies of automobiles and case bodies or other components of various household electric appliances are cut by a band-shaped cutter (a band saw machine) or a disc-shaped cutter (a metal slitting saw), which is provided with a high hardness saw blade, by a grinder cutting method using a grinding tool in which abrasive grains are formed in a disc shape or in a cylindrical shape, or by a gas fusion cutting method using an acetylene gas or the like.
Generally, resin-molded articles are cut by a band saw machine, a metal slitting saw, an end mill, or the like.
In this connection, no cutting device that can cut a member containing different materials such as glass of the CRT or the like, sheet steel, or resin-molded articles or members formed of different materials continuously one after another by rotating one kind of tool (a tool provided with a cutting blade) or by moving it at a high speed has been proposed.
However, in the respective conventional cutting methods described above, there have been the following problems.
(1) In cutting the CRT glass as described above, due to the differences in shape, size, manufacturing processes, or the like of the CRT, the residual stress in the glass also varies and therefore in the method of energizing and heating a heater wire in which the thermal shock is utilized, it is difficult to find out stable cutting and heating conditions or to form a certain stable cut surface.
In the cutting method using a diamond wheel cutter, when the cutting speed is increased, the wear rate of the diamond wheel cutter increases due to frictional heat and therefore the cutting speed is limited. In addition, the diamond wheel cutter is expensive and the cutting amount and the wear rate of the diamond wheel have a close relationship, resulting in high cutting cost.
Furthermore, in the fusion cutting method using a hot gas, the cutting speed is slow and this method is dangerous when combustible materials exist near an object to be cut or a section to be cut. Thus, the applicability of this method is limited.
(2) When the sheet steels are cut using a tool such as a band saw machine, a metal slitting saw, or the like, a cutting blade of the tool is pressed strongly against an object to be cut to cause a continuous shear fracture in the object to be cut, thus cutting and processing the object to be cut.
Since the cutting blade is pressed strongly against the object to be cut, frictional heat is generated greatly at the cutting part. Therefore, the embrittlement and enfeeblement of its cutting edge due to the heat aggravate the abrasion of the cutting edge.
Due to the abrasion of the cutting blade, the cutting speed is lowered considerably and thus is limited. In addition, since the cutting blade is allowed to bite into the object to be cut, a holding mechanism is required to have a high stiffness for holding the tool (a cutter) and the object to be cut, thus requiring a large-scale holding mechanism and a high installation cost.
The grinder cutting method using a grindstone is carried out by causing continuous small shears by cutting blades provided in the abrasive grains. Since the corners (cutting blades) of the abrasive grains are not so sharp and the peripheral speed of the grinder is relatively high, the frictional heat is generated greatly at the cutting part. In order to secure the life span of the grindstone, it is necessary to control the temperature of the cutting part appropriately. Thus, the cutting speed is limited.
In the gas fusion cutting method using a gas such as acetylene, it is important that no combustibles exist in the vicinity of the cutting section in view of safety. Therefore, the applicability of the gas fusion cutting method is limited.
(3) In using a band saw machine, a metal slitting saw, or the like for cutting a resin-molded article or the like, when the cutting speed is increased, the vicinity of the cutting part of an object to be cut starts burning or melts due to the frictional heat generated by the friction with the tool, thus causing a change in physical properties of the object.
(4) When a blade made of a material containing a ferroalloy as a main constituent is used in cutting a metallic magnetic component, the fragments and powder that are produced by cutting an object to be cut are magnetic substances and thus adhere to the edge of the blade. Consequently, the increase in frictional resistance or the damage of the edge lowers the cutting performance of the blade considerably.
(5) It is extremely difficult to cut an object formed of a plurality of members with different physical properties (for example, metal, resin-molded articles, glass, ferrite, or the like) continuously using the same tool.
(6) When the information required for cutting and processing (physical properties or the like) an object is unknown or when an object to be cut is formed of a plurality of members and the shapes and materials of the members hiding behind the surface member are unknown, optimal cutting conditions cannot be found out merely from the image information of the surface and outer shape of the object to be cut. Therefore, the automatic control for optimal cutting is impossible.
In order to solve the above-mentioned problems, the present invention puts a theory to practical use in a cutting device. The theory is a plastic wave theory in which when a high-speed tensile force is applied at least at a critical impact velocity, a fracture occurs immediately at the part where the force has been applied, or a theory in which when a high-speed compressive force is applied at least at a critical impact velocity, the ductility is deteriorated rapidly and thus the part where the force has been applied is broken even by a small distortion (a phenomenon similar to the embrittlement).
Particularly, a cutting device according to the present invention replaces a conventional tool provided with a blade, and in the cutting device an impacting body formed of a hard solid body such as metal is allowed to impact on an object to be cut (hereinafter referred to as xe2x80x9can object to be processedxe2x80x9d or xe2x80x9ca workxe2x80x9d) at a very high speed with a high frequency to generate a plastic wave by the impact energy, thus breaking and removing the part subjected to the impact instantaneously.
In other words, the present invention provides a cutting device based on the following principle: when an impacting body that executes a high speed circular motion impacts on a work at least at the critical impact velocity of the work and then rebounds, the surface of the work in a highly limited area including the part subjected to the impact by the impacting body and its vicinity is smashed (broken) instantaneously into a minute granular state or minute fragments by a high speed compression that occurs together with impact, a high speed tension due to friction, high speed shearing, or the like.
Generally, in processing a work, external forces such as a tensile force, a compressive force, or a shearing force are applied to the work by the movement of a tool and thus the work is distorted or deformed. In this case, when the speed of the tool, i.e. the processing speed, is increased gradually and reaches a certain limitation, the ductility of the work is deteriorated rapidly. This limitation speed is called the critical impact velocity. In the work, the part subjected to the force applied by a tool is broken immediately when the processing speed is increased to the critical impact velocity or more. When utilizing this, by allowing an impacting body to impact on the work at least at the critical impact velocity, only the very surface portion of the work that is subjected to the impact by the impacting body can be broken and removed. By extremely increasing the number of impacts by the impacting body per unit time, this phenomenon can be created repeatedly. Furthermore, by successively changing the position at which the impacting body impacts, only the part on which the impacting body impacts can be removed and processed successively without breaking the portion other than the part in the work. Macroscopically, this can be considered as cutting and processing of the work. According to this cutting method, a relatively smooth cut surface can be obtained.
In order to generate a plastic wave, the impacting body is required to impact on a work at least at the critical impact velocity of the work. Particularly, it generally is preferable that the impact velocity is set to be at least about 139 m/second (about 500 km/hour), more preferably at least about 340 m/second (about 1224 km/hour).
When converted to the peripheral speed of a disc with a diameter of 100 mm, the above-mentioned impact velocities correspond to rotational speeds of at least 26,500 rpm and of at least 65,130 rpm, respectively.
Actually, the critical impact velocity varies depending on the kind of a work. For instance, the critical impact velocities of aluminum, soft steel, stainless steel, and titanium are about 49.7 m/second, 30.0 m/second, 152.3 m/second, and 61.8 m/second, respectively. Therefore, the impact velocity of the impacting body can be changed according to the kind of a work. It is preferred to set the impact velocity of the impacting body to be at least twice, further preferably at least three times, and particularly preferably at least four times as high as the critical impact velocity of the work, because this enables stable cutting.
The impacting body has a through hole and is maintained rotatably by a spindle provided perpendicularly on the rotor with a predetermined fitting gap being provided between the impacting body and the spindle. By providing the fitting gap, the displacement of the impacting body that occurs right after the impacting body has impacted on a work can be absorbed. Preferably, the fitting gap between the spindle for supporting the impacting body and the through hole of the impacting body is set to be at least 2 mm, more preferably about 5 to 10 mm. It is necessary to set the fitting gap to be larger corresponding to the increase in impact velocity of the impacting body. The fitting gap according to the present invention is far beyond the gap value according to the Japanese Industrial Standard (JIS), which generally defines the fitting state between an axis and a bearing, and is two to three orders of magnitude larger than the gap value.
As described above, the processing principle of the present invention is different from a conventional processing principle by utilizing impact. In the conventional processing principle, a cutting blade of a cutting tool is allowed to collide with a work at a low speed (a maximum of about 10 m/second) and the work is deformed in a sequence from elastic deformation to breakage through plastic deformation, thus breaking the surface of the work in a relatively large area.
The impacting body of the present invention is not provided with a sharp cutting blade as in the conventional cutting tool.
Due to the above-mentioned configuration, the cutting according to the present invention is characterized as follows.
(1) According to the smashing (cutting) principle utilizing the high speed compression and high speed tension at least at a critical impact velocity when the impacting body impacts on a work, the frictional heat production at the part to be cut in the work is extremely a little. In addition, the impacting body is air-cooled rapidly by its quick movement and thus the increase in temperature of the impacting body itself also is extremely small.
(2) A cutting tool that executes a rotational motion, a reciprocating motion, or a rectilinear motion is heavily worn away. However, the impacting body of the present invention is subjected to the work hardening by the impact on a work and therefore is hardened as it is used, thus increasing its abrasion resistance.
(3) In the cutting principle of the present invention, the cutting resistance and the frictional resistance are low. As a result, a work is not required to be held and fixed firmly when being cut. In addition, it is not necessary to provide a high stiffness for a spindle for supporting the impacting body, a rotor that rotates at a high speed, a main shaft, a bearing, a robot for holding the main shaft of the rotor, or the like.
(4) By mounting an oscillation detector for detecting an intrinsic oscillatory wave form (or an intrinsic oscillation frequency), which is generated by a rotor depending on the nature of the work when cutting the work, on a multiaxis control robot or the like, processing conditions (the impact velocity of the impacting body, the moving speed, or the like) can be controlled depending on the work to be processed.
(5) Even when a work is formed of a plurality of different members (for example, metal, a resin-molded article, glass, ferrite, or the like) and the inside of the work cannot be seen from the outside, the work can be cut continuously using the same cutting device.
As described above, the cutting device of the present invention has a simple configuration and can achieve the increase in life span and the great improvement in reliability. In addition, since it is not necessary to take into consideration during the cutting process that different materials may be intermixed in a work, the cutting device of the present invention is extremely useful as a smashing or cutting device that is a part of recycling equipment.
Therefore, the present invention can automate scrapping and cutting processes of household electric appliances, automobiles, or the like for the purpose of disposal. According to the present invention, it is not necessary to change the type of cutting tool, processing conditions, or a cutting device according to the kind of an object to be processed or members included in the object. The present invention contributes to the improvement in reliability, the increase in life span of the cutting device and in recycling ratio, the environmental protection, and the efficient use of natural resources.
Specific configurations of cutting devices according to the present invention are described as follows.
A first aspect of the present invention provides a cutting device characterized in that an impacting body is mounted rotatably to a spindle that is provided perpendicularly on a principal plane of a rotor, and the rotor is rotated at a high speed to allow the impacting body to impact on an object to be processed (a work) at least at the critical impact velocity of the object. This cutting device reduces the abrasion of a cutting blade by the impact cutting utilizing a centrifugal force, thus achieving the increase in life span and the improvement in reliability of the cutting device. In addition, the cutting device has no preference for the kind of the object to be processed and enables high speed smashing or high speed cutting.
A second aspect provides a cutting device characterized in that a spindle is provided between a pair of rotors whose principal planes oppose each other, an impacting body is mounted to the spindle rotatably, and the pair of rotors are rotated at a high speed to allow the impacting body to impact on an object to be processed (a work) at least at the critical impact velocity of the object. This cutting device reduces the abrasion of a cutting blade by the impact cutting utilizing a centrifugal force, thus achieving the increase in life span and the improvement in reliability of the cutting device. In addition, the cutting device has no preference for the kind of the object to be processed and enables high speed smashing or high speed cutting.
A third aspect provides a cutting device characterized in that a plurality of cutting units are prepared, each of which is assembled by providing a spindle between a pair of rotors whose principal planes oppose each other and mounting an impacting body to the spindle rotatably, and are mounted to the same main shaft at predetermined intervals, and the main shaft is rotated at a high speed to allow each impacting body to impact on an object to be processed (a work) at least at the critical impact velocity of the object. This cutting device can process a large surface at a time, thus improving the cutting and processing efficiency.
A fourth aspect provides a cutting device characterized in that a plurality of cutting units are prepared, each of which is assembled by providing a spindle between a pair of rotors whose principal planes oppose each other and mounting an impacting body to the spindle rotatably, and are mounted to two axes arranged in parallel, and the two axes are rotated at a high speed in different directions respectively so as to entangle an object to be processed (a work) to allow each impacting body to impact on the object at least at the critical impact velocity of the object. This cutting device has no preference for the material and the kind of the object to be processed and can smash or cut an object at a high speed.
Further, a fifth aspect provides a cutting device characterized in that a plurality of cutting units are prepared, each of which is assembled by providing a spindle between a pair of rotors whose principal planes oppose each other and mounting an impacting body to the spindle rotatably, and are mounted to two axes arranged in parallel so that each of the two axes is provided with a plurality of cutting units at predetermined intervals, and the two axes are rotated at a high speed in different directions respectively so as to entangle an object to be processed (a work) to allow each impacting body to impact on the object at least at the critical impact velocity of the object. This cutting device has no preference for the material and the kind of the object to be processed and can smash or cut an object minutely at a high speed.
A sixth aspect provides processing equipment characterized by mounting a cutting device according to any of the first to third inventions on an arm of a robot with a multiaxis control function. This processing equipment enables three-dimensional processing (processing of a curved surface).
In addition, a seventh aspect is characterized in that the processing equipment of the sixth invention is provided with a control system that detects at least one of an intrinsic oscillatory wave form and an intrinsic oscillation frequency that are generated by the impact of the impacting body on the object to be processed and that controls at least one of the impact velocity and impact direction of the impacting body and the moving speed of the cutting device. The processing equipment enables a constant processing speed or an optimum processing speed for a particular work to be obtained.
An eighth aspect is characterized in that in each cutting device of the first to fifth aspects, the impacting body impacts on the object to be processed at a speed of at least about 139 m/second (about 500 km/hour), preferably with a frequency of at least about 150 times/second. Such a cutting device has no preference for the material and the kind of the object to be processed and can cut an object at a high speed.
A ninth aspect is characterized in that in each cutting device of the first to fifth aspects, the impacting body impacts on the object to be processed at a speed of at least about 340 m/second (about 1224 km/hour), preferably with a frequency of at least about 150 times/second. Such a cutting device has no preference for the material and the kind of the object to be processed and can cut an object at a high speed.
In addition, a tenth aspect is characterized in that in each cutting device of the first to fifth aspects, the impacting body impacts on the object to be processed at a speed of at least twice as high as the critical impact velocity of the object. Such a cutting device has no preference for the material and the kind of the object to be processed and can cut an object at a high speed.